FIG. 1 schematically illustrates an exemplary prior art powertrain 10 for a snowmobile. The powertrain 10 includes an engine 12, a continuously variable transmission (CVT) 14 and a fixed ratio reduction drive 16. A throttle body 18 having a throttle valve 20 therein is connected to air intake ports of the engine 12 to control the flow of air to the engine 12. The CVT 14 includes a driving pulley 22 and a driven pulley 24. The driving pulley 22 is coupled to a crankshaft (not shown) of the engine 12 to rotate with the crankshaft. The driven pulley 24 is coupled to one end of a transversely mounted jackshaft 26 which is supported on a frame (not shown) of the snowmobile through bearings. The transversely mounted jackshaft 26 traverses the width of the engine 12. The opposite end of the transversely mounted jackshaft 26 is connected to the input member of the reduction drive 16 and the output member of the reduction drive 16 is connected to a drive axle 28 carrying sprocket wheels (not shown) that form a driving connection with a drive track (not shown) of the snowmobile.
The driving pulley 22 of the CVT 14 includes a pair of opposed frustoconical belt drive sheaves 30 and 32 between which a drive belt 34 is located. The driven pulley 24 includes a pair of frustoconical belt drive sheaves 36 and 38 between which the drive belt 34 is located. As can be seen, the drive belt 34 is looped around both the driving pulley 22 and the driven pulley 24. The torque being transmitted to the driven pulley 24 provides the necessary clamping force on the drive belt 34 through its torque sensitive mechanical device in order to efficiently transfer torque to the other powertrain components. The effective diameters of the driving pulley 22 and the driven pulley 24 are the result of the equilibrium of forces on the drive belt 34 from a centrifugal actuation system of the driving pulley 22 and the torque sensitive mechanism of the driven pulley 24.
In the powertrain 10, all of the rotating parts rotate in the same direction as the drive track as illustrated by the white arrows. As such, the angular momentums of all of these components add up during operation.
Snowmobiling, especially in soft powdered snow, sometimes requires the snowmobile to be leaned to one side to facilitate turning. In order to cause the snowmobile to lean, the total angular momentum of the rotating parts of the powertrain needs to be overcome. As would be understood, the higher the angular momentum is, the harder it is to lean the snowmobile.
There is therefore a need for a snowmobile powertrain having a lower angular momentum.